Recent Indonesia quake added pressure to key fault

April 19, 2012
By ROBIN McDOWELL , Associated Press

In this April 11, 2012 file photo, people are stuck in a traffic jam as they evacuate to higher ground after a strong earthquake was felt in Banda Aceh, Aceh province, Sumatra island, Indonesia. Residents living in tsunami-scarred Aceh province should prepare themselves for a possible repeat of the 2004 disaster, a leading seismologist said, noting historical data indicates tremendous stresses building up along the explosive fault could unleash again anytime within the next half century. (AP Photo/Heri Juanda, File)

(AP) -- Seismologists say last week's powerful earthquake off western Indonesia increased pressure on the source of the devastating 2004 tsunami: a fault that could unleash another monster wave sometime in the next few decades.

"The spring was pushed a little bit tighter," said Kerry Sieh, director of the Earth Observatory of Singapore.

The timing of another megathrust temblor, if it's on the way, "could have been advanced by a few years," he said.

Last week's 8.6-magnitude earthquake also showed that tsunami-ravaged Aceh province, close to the epicenter, remains unprepared for the next Big One. Though the quake caused little damage, the country's disaster-management chief acknowledged that evacuation efforts were "a big mess."

Indonesia, located on the "Ring of Fire," an arc of volcanos and fault lines encircling the Pacific Basin, has unleashed some of the deadliest seismic events of the past century. But the 9.1-magnitude quake that struck in 2004, triggering a 100-foot-high tsunami and killing 230,000 people, caught scientists off guard because its fault, west of Sumatra island, had long been quiet.

Since then scientists have conducted a flurry of research, looking at tsunami sand deposits, uplifted coral and GPS data. By observing past patterns of quakes, which tend to be cyclical, they better understand what might happen next, though it's impossible to make predictions with any certainty.

The two last behemoth quakes occurred around 1393 and 1450, and Sieh said the 2004 earthquake may be just the first part of a similar couplet.

Stresses loading up on the fault for centuries were relieved only about halfway eight years ago, Sieh. And last week's tremor effectively squeezed the overlapping tectonic plates that form the fault.

"The next megathrust rupture could be in 50 years or in five," he said. "It's impossible to know."

He said a separate section of the fault, hundreds of miles (kilometers) to the south, also could snap within the next 30 years, sending a tsunami slamming into Padang, a low-lying Sumatran city of 1 million.

Last week's quake was a "strike slip" quake, which means it thrust from side to side, not vertically, and therefore did not generate a large tsunami.

Danny Hilman Natawidjaja, a geologist with the Indonesia's Institute of Science, agreed that last week's quake piled a small amount of new stress onto the megathrust, and that "both Aceh and Padang need to be prepared."

"Authorities need to take a good look at what didn't work well last week and find a way to fix it," he said. "Hopefully, this is an opportunity to learn."

Countries along the Indian Ocean have spent millions of dollars installing buoys capable of detecting waves generated by seismic activity, and building up a vast communications network, from alarms on beaches to systems that deliver warnings by TV, radio, Internet and mobile phone text message.

But last week's quake shows that Aceh has a long way to go, even though there was almost no damage and the only deaths were from heart attacks.

Had it been the next Big One, sending waves crashing to shore within 30 minutes, tens of thousands of people could have died in Aceh, where about three-quarters of the 2004 deaths occurred.

Traffic was at a complete standstill as the provincial capital, Banda Aceh, emptied out, people screaming and crying as they piled into cars and motorbikes to try to get to high ground. Many said that after two hours they had only moved six miles (10 kilometers). Some finally gave up, abandoning their vehicles and walking.

"What we found out last week ... was that evacuations were nothing like the simulations," he said.

Among the proposals now being discussed are adding new evacuation routes and expanding existing roads to high ground out of Banda Aceh. Officials also are thinking about building more strong, tall structures along the way so that people unable to get out of town would have better chance of surviving.

Only seven buildings, all built with the help of international aid that poured in after the 2004 disaster, have been set up as emergency shelters. Maarif said some buildings such as shopping malls, mosques and schools should be added to the list of possible safe havens.

(AP) -- A powerful earthquake hit off western Indonesia late Monday, briefly triggering a tsunami warning that sent thousands of panicked residents fleeing to high ground. There were no immediate reports of damage or injuries.

A huge wave-generating quake capable of killing as many people as in the 2004 Indian Ocean tsunami could strike off the Indonesian island of Sumatra, and the city of Padang is in the firing line, a team of seismologists said ...

Recommended for you

The East Antarctic Ice Sheet locks away enough water to raise sea level an estimated 53 meters (174 feet), more than any other ice sheet on the planet. It's also thought to be among the most stable, not gaining or losing ...

Volcanic eruptions are the most spectacular expression of the processes acting in the interior of any active planet. Effusive eruptions consist of a gentle and steady flow of lava on the surface, while explosive eruptions ...

From North Dakota to Ohio to Pennsylvania, hydraulic fracturing, also known as fracking, has transformed small towns into energy powerhouses. While some see the new energy boom as benefiting the local economy and decreasing ...

Environmental scientists from The Open University (OU) have discovered that trees growing in the Amazon floodplains surrounding the Amazon River emit as much methane (CH4) into the atmosphere as all of the world's oceans. ...

It may take until the 2060s to know how much the sea level will rise by the end of this century, according to a new Rutgers University-New Brunswick-led analysis. The study is the first to link global and local sea-level ...

4 comments

The timing of another megathrust temblor, if it's on the way, "could have been advanced by a few years," he said.<<<<<<<<Very true. And so is the opposite. The truth is, we have no way of accurately predicting where and how stresses within the earth's crust originate and spread.Science can only speak in relative generalities about plate movement, particularly on the smaller scale.

Kerry Sieh, went on record in national Geographic with his prediction of another mega thrust event from this fault within the next half century, prior to this recent quake adding to the stress on the fault. That article on tsunamis was well done (I'm not a fan of alot of NG stuff ) and he conveys very clearly his reasoning behind his prediction.

I reiterate: there is no proof that this quake changed the odds of a future large quake. And 50 years? That's throwing darts at a very large wall. The plate movements in this part of the world are, relatively, quite large. So, predicting another large event sometime in the future is pretty easy.

I reiterate: there is no proof that this quake changed the odds of a future large quake. And 50 years? That's throwing darts at a very large wall. The plate movements in this part of the world are, relatively, quite large. So, predicting another large event sometime in the future is pretty easy.

From the article:"Stresses loading up on the fault for centuries were relieved only about halfway eight years ago, Sieh. And last week's tremor effectively squeezed the overlapping tectonic plates that form the fault"Sure it's not proof...but then how would you suggest one prove that they have predicted the future correctly?

Also if you believe that it is easy to predict massive geologic events, I can't wait to read your next paper on the subject.

Please sign in to add a comment.
Registration is free, and takes less than a minute.
Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.